1. Field of the Invention
This invention relates to an apparatus for the automatic sheet (slice) treatment of wafers such as high-purity silicon semiconductor wafers by plasma reaction, and more particularly to the apparatus for the treatment of the wafer by plasma reaction with an improved wafer carrying means.
2. Description of the Prior Art
Recently, etching of a semiconductor wafer, as well as removal by ashing of a photoresist by use of an apparatus for treatment of wafer materials by gas plasma reaction, has become widely available in the field of the semiconductor industry. In the beginning, the apparatus for the treatment of wafer materials by gas plasma reaction was of batch-type, in which 20 to 25 sheets of wafers are placed on a wafer boat for the simultaneous treatment thereof in a reaction tube. As ultra-fine patterning of the circuit, enlargement of the wafer and labor-saving in the production were developed, the drawbacks of the batch-wise apparatus became apparent. These include low processing precision, scattering results from the treatment of wafers among wafers or parts of a wafer, time-taking manual handling of wafers for setting and damage of the wafer due to manual handling thereof, especially in the case of a large-sized wafer. These are the problems of the art which are to be solved.
In order to overcome the drawbacks of the batch-type apparatus as mentioned above, U.S. Pat. No. 4,151,034, for example, discloses a continuous gas plasma etching apparatus. In this apparatus, a workpiece is subjected to etching while the workpiece is on an endless belt turning in a reaction chamber to pass through the reaction chamber so that undesirably scattering results from the etching treatment are obtained. U.S. Pat. No. 4,189,923 also discloses an automatic apparatus for the treatment of wafer materials by plasma reaction, in which all elements of the apparatus are installed on an inclined base table to effect the downward movement of the wafer, and the wafer is to be stopped as required by a wafer stopper such as a nib or rotary block. Accordingly, there is the drawback that the wafer is liable to be damaged due to the stopper on stopping the wafer.
U.S. Pat. No. 4,094,722 also discloses a continuous etching apparatus for etching a semiconductor element using a plasma, in which an activated gas from a gas plasma is conducted into an airtight etching chamber and a rotatable support plate having a semiconductor element holder rotates between a semiconductor element feeding chamber and the etching chamber in order to continuously feed the semiconductor elements in large amounts. However, an airtight hollow chamber must be provided to contain the rotatable support plate because the etching treatment is effected under airtight conditions and a hatch, which is opened and closed as required, is also required to be provided in a separate position from the airtight etching chamber so that a semiconductor feeding means may be provided therebeneath.
Further, the present inventors propose an apparatus for the treatment of a wafer by plasma reaction in U.S. Pat. No. 4,208,159 in which a sheet by sheet treatment of a wafer is effected continuously with such remarkable advantage that the scatter resulting from the treatment of wafers becomes narrower, the scatter from the treatment of wafers among both central and peripheral portions of a large-sized wafer also becomes narrower, ultra-fine patterning of the circuit becomes available, the apparatus is labor-saving, damages of a large-sized wafer during treatment operations are eliminated; thus, overcoming the drawbacks of the conventional apparatus. Further, the treating time per one sheet of wafer is shortened. However, the apparatus is provided with a pair of pick-up driving mechanisms of revolving or parallel running-arm type which suck and release the wafer for carrying in a wafer carrying means. In order to avoid touching the clean resist surface, it is necessary to pick-up the wafer on its circumference, and this is important. This has the disadvantages that pick-up heads are required to be exchanged depending upon the size of the wafer materials, and pressure control on sucking portions of the pick-up must be effected depending on the weight of the wafer materials. Difference in weight of wafers after processing, especially large wafers, the weight difference will be big, and cannot be pick-up, or there will be a disadvantage of breakage due to strong suction. In other system in which wafers are blown up by means of gas being spurted from tiny holes, but this system will invited dirts and foreign matters onto wafers. Large wafers present difficult problems.